This invention relates to an engine control method and apparatus and more particularly to an improved, simplified, highly effective and yet low cost arrangement for such control.
In internal combustion engines, a wide variety of systems and methodology are employed for engine control. Generally, smaller and lower volume engine applications incorporate generally less sophisticated controls than those employed on larger production volume engines such as automotive engines. Even in the small displacement lower production volume engines, for example those used in motorcycles, the engine control can become quite complicated.
For example and as shown in FIG. 1 the spark control for a motorcycle engine is shown schematically. The control arrangement is intended to control the firing of a spark plug 21 associated with an internal combustion engine 22 that powers the motorcycle, which is not shown in this figure, but which may be of a construction as generally shown in FIG. 3. An amplified spark voltage is applied to the spark plug 21 from an ignition coil 23, which, in turn, is controlled by an ignition timing control arrangement, indicated schematically at 24. This timing control arrangement 24 receives the inputs from a number of engine-associated sensors. These include a crankcase rotational speed sensor 25 which may comprise a pulser coil and a throttle position sensor 26, which is coupled to the throttle control mechanism for the engine 22 and inputs a signal to the control 24 indicative of engine load and/or operator demand.
Electrical power is provided to the ignition control circuit 24 from a battery 27 through a main switch 28. This battery power is applied to a power source circuit 29 of the control 24 and specifically to an electronic circuit 31 which may comprise a microprocessor.
The output from the engine speed sensor 25 is transmitted to a rotational speed detector circuit 32, which counts the number of pulses generated in a time period so as to determine the rotational speed of the crankshaft of the engine 22.
This outputs a speed signal N to an ignition timing determining circuit, indicated at 33. In addition, the throttle position sensor 26 inputs a signal to a throttle position detector circuit 34. This detector circuit 34 outputs a signal a to a throttle opening calculating circuit 35. This, in turn, outputs a throttle angle position xcex8 to the ignition timing determination circuit 33.
From these inputs, the ignition timing determining circuit outputs a signal at a time determined from maps contained in a memory of the circuit 31 to an ignition circuit 36 which may be of the capacitor discharge type so as to output an electrical output xe2x80x9cixe2x80x9d to the coil 23 which is stepped up by the coil 23 to a value xe2x80x9clxe2x80x9d for firing the spark plug 21 in a well-known manner.
FIG. 2 is a graph showing one of the maps which may be incorporated in the circuit 31 and shows how the spark timing is varied in response to engine speed for given load as determined by the throttle opening circuit. There may be a family of such curves so as to vary the ignition timing in response to both throttle position and engine speed.
Rather than using a throttle position sensor, load may be sensed by intake manifold vacuum. Either method, however, requires added sensors, transducers and circuitry.
It has been found that merely using engine speed and load as detected by something such as a throttle position or intake manifold vacuum sensor does not actually provide as good a control as desired. That is, these two factors by themselves may not be sufficient to provide the desired degree of control.
Although systems have been provided for automotive applications wherein more sophisticated controls are employed, this further adds to the cost of the system and does not always provide the optimum results.
There have also been other devices than throttle position sensors or vacuum sensors for sensing intake manifold vacuum for determining engine load. It also has been determined that engine load may be found by comparing engine speed from one revolution to another.
However, these systems also tend to be complicated and do not lend themselves particularly low production volume, low cost vehicle applications. They also have the disadvantage of requiring a plurality of different types of sensors.
Other arrangements have been proposed wherein engine speed is measured for less than one complete revolution of the engine and variations from cycle to cycle have been employed to determine engine load. These systems, however, have for the most part, required multiple sensors and also require some delay from the sensed conditions before adjustment is being made.
It is, therefore, a principal object to this invention to provide an improved engine control system wherein the number of sensors employed for achieving optimum engine control is substantially reduced.
It is a further object to this invention to provide an arrangement for controlling an engine system utilizing only a single sensor and a single timing mark associated with a driven engine shaft so as to substantially reduce the costs, without significantly decreasing the efficiency or the obtaining of an optimum control.
Also, it should be understood although a specific example of engine ignition timing control is disclosed and has been described, other engine systems also may be controlled in a like manner such as fuel control with either fuel injection or other forms of fuel supply and throttle control for fly-by wire throttle systems. Other engine control applications with which the invention may be employed will present themselves to those skilled in art from the following description.
A first feature of this invention is adapted to be embodied in an internal combustion engine control system and a method for operating an engine by controlling a system of the engine. The engine has a driven shaft and a sensor arrangement is associated with the driven shaft for sensing the instantaneous rotational speed of the driven shaft during the rotation of the driven shaft for less than a complete rotation and for sensing the rotational speed of the driven shaft for a complete revolution that includes the measured less than complete rotation. In accordance with the method and apparatus, the engine system is controlled from these measurements.
Another feature of the invention is adapted to be embodied in a four-cycle internal combustion engine control system for controlling the system of the engine. In accordance with the method and apparatus, the engine has a driven shaft and a sensor arrangement is associated with the driven shaft for sensing the rotational speed of the driven shaft. The rotational speed of the driven shaft during a revolution containing a compression stroke and during a revolution containing an exhaust stroke are made. The engine is controlled from these measurements.
Another feature of the invention is adapted to be embodied in a method and apparatus for an internal combustion engine control system for controlling a system of the engine. The engine has a driven shaft and sensor is associated with the driven shaft for sensing two rotational conditions of the driven shaft during a first rotation thereof. The same two rotational conditions are sensed during the immediately succeeding rotation of the driven shaft and the engine system is controlled on the third rotation of the driven shaft from these measurements.